Research and Markets have already released a report arguing about the benefits of MSR-BS. Last year Ericsson released the RBS 6000 series products that has MSR support. Huawei and Nokia Siemens Networks are also working on similar products under different guises. Martin has blogged about this topic as well earlier in case you want to refer to.
According to Research and Markets report the terms used for this technology is Multi-Standard Radio Base Station (MSR-BTS/MSR-BS), Multi-Mode Radio Base Station (MMR-BTS/MMR-BS) and Multi-Radio Access Technology (Multi-RAT). The name in standards usually is MSR-BS.
So what is MSR-BS? The 3GPP definition is: Base Station characterized by the ability of its receiver and transmitter to process two or more carriers in common active RF components simultaneously in a declared RF bandwidth, where at least one carrier is of a different RAT than the other carrier(s).
In very simple terms, a single Base Station will be able to simultaneously transmit different radio access technologies from a single unit. So a unit may be for example transmitting GSM, WCDMA 2100 and LTE 2600 simultaneously.
The number of technologies supported by a BTS will be an implementation choice. With technology maturing it wont be surprising to have upto 4-5 different technologies in a MSR-BS in the next five years.
The advantage the mobile operator will have will not only be monetary but there will be possibility of space saving. But as the old english proverb says, they will be "putting their eggs in a single basket". If one unit stops working then the coverage in the area goes down. There may not be an option to fallback on different technology.
The way this MSR-BS are implemented will be definitely based on Software Defined Radios (SDR). The advantage with SDR will be that in different parts there is a slight frequency variation for different technologies like GSM-850 is specific to USA whereas the rest of the world uses GSM-900. These small variations will easily be customisable with these MSR-BS and optimisations wont be too far off.
Different Band Categories have been defined for different scenarios. For example Band Category 1 involves deplyment where GSM wont be present. Only LTE and WCDMA is present there. Band Category 2 involves frequency bands where GSM, EDGE, WCDMA and LTE may be present. Band Category 3 is designed with TDD and TD-SCDMA in mind.
More information as and when available